Control apparatus



Feb. 12,1946. M, E, cHANbLER 2,394,664

-CONTROL APPARATUS Filed Jan. 25, 1944 MIXTURE T0 ENGINE INVENTOR MLTWE MERE AGENT Patented Feb. 12, 1946 UNITED STATES PATENT OFFICE CONTROL APPARATUS Milton E. Chandler, New Britain, Conn., assignor to Chandler-Evans Corporation, South Meriden, Conn., a corporation of Delaware Application January 25, 1944, Serial No. 519,611 6 Claims. (Cl. 261-30) conditions. In engines such as aircraft engines,

where the throttle is located at some distance from the pilot's control lever and is connected to that lever by a rather complicated linkage, it is also desired to provide some means to limit the minimum power output of the engine upon failure of the control linkage.

It is therefore an object of the present invention to provide improved means for limiting the movement of the throttle of an internal combustion engine.

Another object is to provide means for limiting the opening movement of the throttleof-an internal combustion engine so'as to provide a sub stantially constant maximum air flow to the engme.

Another object is to provide improved means for controlling the throttle of an internal combustion engine so as .to secure a substantially constant flow of air to the engine.

Another object is to provide improved means responsive to the position of the throttle for controlling the fuel fiow under idling conditions.

A further object is toprovide improved means for preventing closure of the throttle beyond a partially open position in the event that the manual control linkage fails.

A still further object is to provide an arrangement of the type described in which the idling control mechanism serves to operate the throttle to a partially open position upon failure of the manual control linkage.

Other objects and advantages of the present invention will become apparent from a consideration of the appended specification, claims and drawing, in which the single figure-represents a carburetor for an internal combustion engine provided with control apparatus embodying the prinfold of the engine. In certain cases the supercharger may be upstream from the inlet l2, or two superchargers may be used, one in each place.

The Venturi restriction I4 produces a pressure differential between the inlet I2 and the throat of the restriction which varies in accordance with the square of the velocity of the air passing thru the restriction. Since the cross-section of the venturi is constant, this pressure differential may be taken as a measure of the volume of air flowing thru the passage.

In order to control combustion conditions within the engine, it is necessary to control the fuel flow in proportion to the air flow. The fuel flow is controlled in accordance with the mass of air .fiowing, rather than its volume, because the density of the air varies in accordance with its pressure and temperature, which are in turn affected by external atmospheric conditions and by the altitude at which the aircraft is flying.

As previously stated, the pressure difierential between the entrance I! and the throat of venturi l4 varies as a function of the volume of air flowing thru the venturi. In order to obtain a pressure differential varying'as a function of the mass of air flowing thru the venturi I4, the pressure differential between entrance I2 and the throat of venturi I4 is utilized to create an air flow thru a secondary air passage extending from entrance l2 to the throat of venturi H. A plurality of impact tubes 22 are provided, whose open ends project into the entrance l2 to receive the impact of the entering air. The secondary air passage may be traced from entrance I2, thru tubes 22, a passage or vent ring 24 interconnecting the impact tubes, a conduit 26, a chamber 28 in a pressure meter generally indicated at 30, a restriction 32, a chamber 34 in the pressure meter 30, a conduit 36, past a valve 38 into a chamber 40, and thence thru a conduit 42 to the throat of venturi It.

The valve 38 is controlled by a sealed bellows 44 mounted in the chamber". The bellows 44 is fixed at one end, so that the position of the sussuw MAR 16 I948 sure drops, one across the restriction 32 and the other across the valve 38. The valve 38 is positioned in accordance with the density of the air flowing thru the passage I5. Valve 38 is moved toward open position as the air density increases and toward closed position as the air density decreases. If the volume of air flowing thru passage I remains constant and the air density de the chambers 28 and 34. The force applied to diaphragm 46 is transmitted to a valve 48, on which it acts in a closing direction.

The fuel enters the carburetor from a fuel pump or other source of fuel under superatmospheric pressure thru a conduit 58 and flows thru a valve 52 in a pressure regulator generally indicated at 54, a conduit 56, anidle control I 26,

a conduit 51, a mixture control generally indicated at 58, a jet system 68, a conduit 62, a valve 64 in a second pressure regulator 66, and a conduit 68 to the fuel discharge nozzle I8.

The pressure regulator 54 includes a diaphragm I8 separating a pair of expansible chambers 12 and 14 and connected at its center to the valve 52.

A spring 16 biases the valve 62 toward open position. A restriction I8 connects the chambers I2 and 14.

A portion of the fuel entering pressure regulator 54 flows thru chamber I4, restriction I8,

chamber 12, a conduit 88; a chamber 82 in the pressure meter 38, past the valve 48, and thru a conduit 84 to a suitable drain, which may, for example, empty into the main air passage I5. If desired, the drain may be connected to the main fuel tank, or the full flowing thru it may be otherwise disposed of.

The pressure meter 38 includes a diaphragm 86 separating the chambers 34 and 82 and a diaphragm 88 separating the chamber 28 from a fourth expansible chamber 98. The valve 48 is biased toward closed position by a spring 92.

The chamber 98 is connected thru a conduit 94 to the fuel conduit 62 downstream from the jet system 68. The pressure in chamber 98 is therefore the same as that in the fuel line downstream from the jet system. The pressure in chamber 82 is the same as that in chamber I2 of pressure regulator 54. The pressure in chamber 12 differs from the pressure in chamber 14 by a fixed amount which depends on the strength of spring I6. Therefore the pressure in chamber I2 is a measure of the pressure on the upstream side of the jet system 68. For any given constant cross-sectional area of the fuel passage thru the jet system 68, the pressure differential across it is a measure of the fuel flow thru it. This pressure differential, or rather a smaller pressure differential which is a measure of the pressure differential across the jet system, is applied thru the diaphragm 86 and 88 of pressure meter 38 to the valve 48, on which it acts in an opening direction.

From the foregoing, it may be seen that the valve 48 is positioned in accordance withthe balance between two forces, one of which varies in accordance with the mass of air entering the carburetor, and the other in accordance with the mass of fuel entering the carburetor. Furthermore, the valve 48 controls the mass of fuel entering the carburetor, since it controls the pressure in chamber 82. The pressure in the chamber 82 is transmitted to chamber I2 of pressure regulator 54 where it controls the position of valve 52 and hence the pressure on the upstream side of the jet system 68. The pressure on the upstream side of jet system 68 is therefore varied as a function of the mass of air flowing to the engine for combustion purposes.

The pressure regulator 66 operates to maintain a substantially constant pressure on the downstream side of the jet system 68 andthereby to prevent variations in pressure at the fuel discharge nozzle I8, which may be due to operation of the throttle or to variations in engine speed, from reaching the downstream side of the jet system and affecting the fuel flow.

Since the pressure on the downstream side of the jet system 68 is held constant and the pressure on the upstream side is varied as a function of the air flow, it may be seen that for a given constant cross-sectional area of the jet system, the fuel flow is proportioned to the air flow. The mixture control 58 may be operated to vary the crosssectional area of the jet system and hence to vary the fuel to air ratio.

The pressure regulator 66 includes a pair of expansible chambers 96 and 98 separated by a flexible diaphragm I88, which is attached at its center to the valve 64. A spring I82 biases the valve 64 toward closed position. The chamber 96 is connected thru a conduit I84 to the conduit 26 and thence thru the vent ring 24 and impact tubes 22 to the air entrance I2. The chamber 98 is connected to the fuel conduit 62.

The mixture control 58 includes a disc valve I86 flxed on a shaft I08. The disc valve I86 controls the flow of fuel thru ports opening into conduits III) and H2 which lead into the jet system 68. When the disc I86 is in the position illustrated in full lines in the drawing, fuel can flow to the jet system only thru the conduit II 8. This full line position of the disc valve I86 is known as the lean position of the mixture control 58. When the disc valve I86 is in the dotted line position shown in the drawing, the fuel can flow thru both the conduits H8 and H2. The dotted line position of disc valve I86 is termed the rich position of the mixture control.

The conduit II8 conducts fuel either thru a fixed restriction or jet H4, or thru a restriction II6 controlled by a valve II8 biased to closed position by a spring I28. The conduit I I2 conducts fuel to a fixed restriction I 22. Fuel flowing thru the restrictions H6 and I22 also flows thru another restriction I24 which determines the maximum flow thru restrictions H6 and I22.

The valve II8 opens only at high pressure differentials across the jet system to increase the fuel to air ratio under heavy load conditions.

The idle control I26 includes a valve I28 attached to the center of a diaphragm I38. A spring I32 biases the valve I28 in an opening direction. A stop I34 is provided to limit the open-' ing movement of valve I28. An elongated stem I 36 extends outwardly from the side of diaphragm I38 opposite the valve I28.

The throttle I6 is fixed on a shaft I38. An arm opposite end is pivotally attached to an arm I44 assess;

A spring I58 biases the arm I40 into engagement with the stop I54.

The opening movement of the throttle is limlied by a stop mechanism generally indicated at I58. Th stop mechanism I58 includes a bellows closure of valve 48 increases the pressure in chamber 82 of pressure meter 80 and hence in chamber 12 of pressureregulator 54. This causes an opening movementof valve 82 until a balancing increase is produced-In the pressure in chamber 14, which is the same same pressure on the upstream side of the iet system 80. Furthermore, the spring I8 of pressure regulator 54 biases valve 52 in an opening or fuel flow increasing direction.

As the throttle I8 approaches its idling position, the link I44 is rotated clockwise and its lower I80 whose interior is connected thru a conduit I82 to the fuel conduit 58. A compression spring I84 biases the free end of bellows I80 for movement to the left. A stop member I88 is attached to the free end of bellows I80, and the opposite end of stop member I88 extends into the path of movement of the upper end of arm I44.

In order to move the throttle toward open position, the pilot moves his control lever so as 'to move link I82 to the right. This causes a counterclockwise movement of lever I50. Since the arm I 40 is held in engagement with stop I54 by spring I58, it follows the counterclockwise movement of lever I50. Since the arm I40 is fixed on the shaft I38, the latter is-also rotated. thereby moving the throttle I8 in an opening direction.

This opening movement can continue under the control of the manually operated link I52 until the upper end of arm I44 engages the stop member I88. Thereafter, if the link I52 is moved further to the right, the arm I40 does not follow the lever I50, but the spring I58 is stretched and the stop I54 separates from the arm I40.

The position of the throttle at such a time is determined by the position of stop I 68. The position of stop I88 in turn depends upon the pressure in conduit 58 and hence on the regulated pressure in chamber I4 of pressure regulator 54. As previously described, the pressure in chamber I4 varies as a function of the mass of air flowing to the engine thru the venturi I4.

Under these conditions. the throttle I8 is controlled to maintain a substantially constant air flow. If the air flowing to the engine should increase, there would be a resulting increase in the pressure in chamber I4. This increased pressure in chamber I4 is transmitted to bellows I80 where it acts thru the stop I88 to move the throttle I8 in a closing direction, thereby decreasing the air flow. Therefore the system tends to maintain a constant air flow. The value of this air flow may be adjusted by changing the tension of spring I84 and hence the position at which stop I88 is maintained for a given value of air flow. Although no means is illustrated for changing the tension of spring I84, such means are common and may readily be provided.

At low air flows, such as are encountered under idling conditions. the pressure differential set up by the venturi I4 tends to be erratic, and is not a reliable indication of the volume of air entering the engine. Provision is made to transfer control of the fuel flow to the throttle at such times. The spring 92 in the pressure meter 30 acts on valve 48 in a closing direction. when the differential pressure acting on diaphragm 48 is small, as under low air flow conditions, the spring 82 is end I48 engages the end of valve stem I88 and operates the idle control I28 so as to move valve I28 in a closing direction. Under such conditions, the quantity of fuel supplied to the engine is determined by-the throttleposition as that position is reflected in the position of valve I28. This is in contrast to the operation-.of the system at -higher air flows when the fuel-supply is determeasured by pressure. meter 80.

- from the scope of the invention as the predominating force acting on valve 48. A

closing movement of valve 48 causes an increase in the fuel flow thru the main fuel line, since the mined. by themass of air entering-the engine as If the linkage connecting the link I52 with the pilots control lever should fail, then the maximum opening position of the throttle would be limited by the stop mechanism I50 and the maximum closing position would be limited by valve stem I38. Therefore the engine would continue to-operate and drive the aircraft, even though its speed of operation could not be predicted. This might .be' of considerable advantage to the occupants of the. aircraft.- For example, under combat conditions, it might enable the aircraft to return to-its base even though the throttle control was not operative.- The throttle could not move to its fully closed position and cut oil. the engine, nor coulcl it move to its fully open position and cause the engine to become overheated.

While, Ihave shown and described a preferred embodiment of my invention, it will be readily understood by those-skilled in the art that other modifications may be made without departing defined in the appended-claims. I claim as my invention:

1. Control apparatus for an internal comlbus- :tiOl'i engine comprising throttle means for con trolling the flow of air tosaid engine, manually movable means for positioning said throttle means, stop means for limiting the opening movement of said throttle means, spring means permittin additional movement of said member after said throttle means engages said stop means. a conduit for fuel flowing to said engine, means responsive to the quantity of air flowing to said engine for controlling a fuel pressure in said conduit, means responsive to said controlled pressure for positioning said stop means, valve means in said fuel conduit, means biasing said valve means toward-open position, abutment means associated with said valve means and said throttle means and adapted to engage when said throttle means is adjacent its closed position to cause a following movement of said valve means. said biasing means being efiective upon failure of said manually movable means to move said throttle means to a partially open position.

2. Control apparatus for an internal combustion engine, comprising a first conduit for air flowing to said engine for combustion purposes, throttle means for controlling the flow of air thru said conduit, a second conduit for fuel flowing to said engine, means responsive to the quantity of air flowing thru said first conduit and effective when said quantity exceeds a predetermined value to control a pressure in said fuel said throttle means is in a, position corresponding to a. quantity of air less than said predetermined value. g

3. Control apparatus .for aninternal combustion engine, comprising adirst conduit for air flowin to said engine for combustion p pflses, throttle means'for controlling the flow. of air thru said conduit, manually movable means for. positioning said throttle means, asecond conduit for fuel flowing .to said engine, means responsive to the quantity of air flowing thru said first conduit and effective when said quantity exceeds a predetermined value to control the flow thru said fuel conduit, valve means in said second conduit for additionally controlling the fuel flow themthru, spring means biasing said valve means toward open position, means responsive to the pressure in said fuel conduit and acting on said valve means in an openingvdirection, and a member connected to said throttle means for movement therewith, said member being positioned adjacent said valve means and adapted to engage said valve means to cause a following movement thereof whenever said throttle means is in a position corresponding to a quantity of airless than said predetermined value, said spring means and said fuel conduit pressure being effective upon failure of said manually movable means to move said throttle means to a partially open position.

4. Control apparatus for an internal combustion engine, comprising throttle means for controlling the flow of air thru said conduit, manually movable means for positioningsaid throttle means, a second conduit for fuel' flowing to said engine, valve means in saidsecond conduit for aspen controlling the fuel flow therethru, spring means biasing said valve means toward open position, and a member connected to said throttle means for movement therewith, said member being positioned adjacent said valve means and adapted to engage said valve means to cause a following movement thereof whenever said throttle means is in a position adjacent its closed position, said spring means being effective upon failure of said manually movalble means to move said throttle means to a partially open position.

5. Control apparatus for an internal combustion engine in an aircraft, comprising throttle means for controlling the flow of air to'said engine for combustion purposes, a manually movable control member remote from said throttle means, linkage connecting said member and said throttle means, a conduit for fuel flowing to said engine. valve means in said conduit for controlling the fuel flow therethru, spring means biasing said valve means toward open position, and a member connected to said throttle means for movement therewith, said member being positioned adjacent said valve means and adapted to engage said valve means to cause a following movement thereof whenever said throttle means is in a position adjacent its closed position, said spring means being effective upon failure of said linkage to move said throttle means to a partially open position.

6. Control apparatus for an internal combustion engine, comprising throttle means for controlling the flow of combustion air to said engine, means for positioning said throttle, a member connected to said throttle for concurrent movement therewith, a pair of abutments for engaging said member so as to limit the movement of said throttle in either direction from an intermediate position, resilient supporting means for one of said abutments so that said throttle may be moved beyond the limiting position established thereby, said abutments and said resilient supporting means being, eflective on failure of said throttle positioning means to confine said throttle to an intermediate range of positions. MILTON E. CHANDLER. 

